1. Field of the Invention
The present invention relates to an apparatus for producing a semiconductor device, and particularly to a cathode roller mechanism provided in an electrolytic apparatus for electrolyzing the lead frame of a semiconductor device.
2. Description of the Related Art
The surfaces of the external leads of insulating sealed semiconductor packages are generally plated by solder electroplating for the purpose of imparting corrosive resistance to the external leads and sufficiently soldering them. Electrolysis is effected in the above solder electroplating process and pretreatment processes such as electrolytic degreasing and deburring processes. A cathode roller mechanism is provided in an electrolytic cell which is filled with an electrolyte used for electrolyzing a semiconductor device. The cathode roller mechanism carries the semiconductor device in the electrolyte while the lead frame of the semiconductor device is being electrically connected to an external circuit to be made a cathode under electrical continuity by the cathode roller mechanism.
FIG. 1 is a schematic side view of a conventional cathode roller mechanism disclosed, for example, in Japanese Utility Model Laid-Open No. 63-24273. In a cathode roller mechanism 10, a lead frame 40, which is integrated with a molded portion 41 is carried in an electrolyte (not shown) by the rotation of a cathode roller 20 and a pressure roller 30 while being held between these rollers 20 and 30, and the lead frame 40 is made a cathode under electrical continuity by the cathode roller 20. The cathode roller 20 comprises a cathode roller shaft 21, a tapered roller body 23 and an electrically conductive stopper 26. The cathode roller shaft 21 is a shaft which is made of an electrically conductive material so that it can conduct the electricity. The cathode roller shaft 21 has the function to rotate the portion including the tapered roller body 23 and the electrically conductive stopper 26 and makes the lead frame 40 a cathode through the electrically conductive stopper 26 during electrical conduction of a cathode current. The tapered roller body 23 has a tapered surface 22, which also serves as a mounting surface for the lead frame 40, between a small diameter portion 24 and a large diameter portion 25. The tapered roller body 23 is formed of an insulating material. The electrically conductive stopper 26 has a diameter which is larger than the diameter of the small diameter portion 24 of the tapered roller body 23 and is made of a electrically conductive material. The electrically conductive stopper 26 is provided at the small diameter portion 24 side of the tapered roller body 23 so that one end of the lead frame 40 contacts with the stopper 26. The stopper 26 is also electrically connected to the cathode roller shaft 21. The pressure roller 30 comprises a roller shaft 31 and a roller body 32. The roller body 32 is made of a sponge so as to have elasticity and has the function to press the lead frame 40 on the tapered surface 22 of the cathode roller 20 so as to cause the lead frame 40 to be easily carried in the horizontal direction. In practice, many cathode roller mechanisms 10 are provided in such a manner that they are arranged in the direction of conveyance of the lead frame 40 (not shown). The lead frame 40 is thus successively transferred in the horizontal direction while being made a cathode.
A brief description will now be given of the operation.
Since the tapered roller body 23 of the cathode roller 20 has the tapered surface 22, the lead frame 40 is moved along the tapered surface 22 in the direction shown by the arrow R in FIG. 1 and is made a cathode owing to the contact between the conductive stopper 26 and one edge of the lead frame 40. The lead frame 40 is also elastically pressed on the tapered surface 22 by the roller body 32 of the pressure roller 30. This stabilizes the connection between the edge of the lead frame 40 and the conductive stopper 26. The cathode roller mechanism 10, therefore, carries the lead frame 40 while making it a cathode.
However, the conventional cathode roller mechanism configured as described above has a problem in that no positive measure is taken to prevent a deviation of the lead frame from the cathode roller mechanism during the conveyance, and particularly a deviation of the lead frame from a predetermined position when it enters the cathode roller mechanism.